一些可能有用的Android代码

没地儿放它们。

渐隐重启Activity

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// 1
startActivity(Intent(this, MainActivity::class.java))
finish()
overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out)

// 2
startActivity(Intent(this, MainActivity::class.java),
ActivityOptions.makeCustomAnimation(this, android.R.anim.fade_in, android.R.anim.fade_out).toBundle()
)
finish()

RingtoneManager

Note that the list of ringtones available will differ depending on whether the caller has the {@link android.Manifest.permission#READ_EXTERNAL_STORAGE} permission.

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val intent = Intent(RingtoneManager.ACTION_RINGTONE_PICKER)
.putExtra(RingtoneManager.EXTRA_RINGTONE_TITLE, "Hello")
.putExtra(RingtoneManager.EXTRA_RINGTONE_TYPE, RingtoneManager.TYPE_ALL)
.putExtra(RingtoneManager.EXTRA_RINGTONE_SHOW_SILENT, true)
.putExtra(RingtoneManager.EXTRA_RINGTONE_SHOW_DEFAULT, true)
.putExtra(RingtoneManager.EXTRA_RINGTONE_DEFAULT_URI, Uri.EMPTY)
.putExtra(RingtoneManager.EXTRA_RINGTONE_EXISTING_URI, Uri.EMPTY)
startActivityForResult(intent, 0)

onActivityResult,

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val uri = data?.getParcelableExtra<Uri>(RingtoneManager.EXTRA_RINGTONE_PICKED_URI)
val name = if (uri != null) {
val rng = RingtoneManager.getRingtone(this, uri)
if (rng != null) {
rng.stop()
rng.getTitle(this)
} else {
getString(R.string.unknown)
}
} else {
getString(R.string.unknown)
}

文件选择

来自Codelab的一段代码.

需要READ_EXTERNAL_STORAGE权限。

RecyclerView头部视差显示

使第一个View渐隐退出Window。

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list.addOnScrollListener(object :RecyclerView.OnScrollListener(){
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
val view = recyclerView.getChildAt(0)
if (view != null && recyclerView.getChildAdapterPosition(view) == 0) {
view.translationY = view.top / 3f
view.alpha = 1 - -view.top.toFloat() / view.height
}
}
})

ADB查看当前Activity

  1. adb shell "dumpsys window w | grep name="
  2. 栈顶:adb shell dumpsys activity | grep "mFocusedActivity"
  3. 栈顶Fragment:adb shell dumpsys activity your.package.name

ADB截屏并保存

adb shell screencap -p | perl -pe 's/\x0D\x0A/\x0A/g' > screen.png

或者

adb exec-out screencap -p > screen.png

Grab Android screenshot to computer via ADB

让一个Activity有类似Android O或P彩蛋一样的背景。

设置theme为android:theme="@android:style/Theme.Wallpaper.NoTitleBar.Fullscreen"

给Layout添加Ripple

  1. 创建ripple_press.xml

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    <?xml version="1.0" encoding="utf-8"?>
    <ripple xmlns:android="http://schemas.android.com/apk/res/android"
    android:color="@android:color/white">
    <item android:id="@android:id/mask">
    <shape android:shape="rectangle">
    <solid android:color="@android:color/white" />
    </shape>
    </item>
    </ripple>
  2. 在Layout中使用

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    <com.google.android.material.card.MaterialCardView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:clickable="true"
    android:focusable="true">

    <!-- ... -->

    <View
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:foreground="@drawable/ripple_press" />

    <!-- ... -->

    </com.google.android.material.card.MaterialCardView>

    clickablefocusable很重要,View之前的View会有Ripple效果,之后的View则没有。

AutoClearedValue

https://github.com/googlesamples/android-architecture-components/blob/master/GithubBrowserSample/app/src/main/java/com/android/example/github/util/AutoClearedValue.kt

带清除按钮的EditText

来自Best Practices for Using Text in Android (Google I/O’19)

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<LinearLayout
android:addStatesFromChildren="true"
android:background="?editTextBackground">

<EditText android:background="@null" />

<ImageButton ... />

</LinearLayout>

Custom View中的onSaveInstanceState

Android didn’t manage the onSaveInstanceState/onRestoreInstanceState if no id is set to the view.

?attr, ?android:attr, ?colorPrimary, ?attr/colorPrimary…

https://developer.android.com/guide/topics/resources/providing-resources#ResourcesFromXml => Referencing style attributes`

File - Mark As Plain Text

重构时很有用,不会影响VS。

FragmentManager.setCustomAnimations()‘s Parameters

  • @AnimatorRes @AnimRes int enter: 应用到动画中进入屏幕的Fragment
  • @AnimatorRes @AnimRes int exit: 应用到动画中退出屏幕的Fragment
  • @AnimatorRes @AnimRes int popEnter: 应用到popBackStack时动画中进入屏幕的Fragment
  • @AnimatorRes @AnimRes int popExit: 应用到popBackStack时动画中退出屏幕的Fragment

Kotlin in and out

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// 一个RecyclerView.ViewHolder子类的List
// 因为不知道到底是哪个子类,所以不能安全的添加或修改
// 但肯定能拿到一个RecyclerView.ViewHolder
// 只能拿,所以叫out,Java里叫extends
val outList: MutableList<out RecyclerView.ViewHolder> = mutableListOf()

// 一个RecyclerView.ViewHolder父类的List
// 因为不知道到底是哪个父类,所以只能强行拿到顶层的Any?
// 但是可以随便添加或修改RecyclerView.ViewHolder及其子类
// 只有添加或修改方便,所以叫in,Java里叫super
val inList: MutableList<in RecyclerView.ViewHolder> = mutableListOf()

clipToPadidng

Enables our items to still be drawn within the parent's padding.